In an older home a typical roof rafter can range between 2 4 s to 2 8 s.
2x4 attic joists upgrade insulation.
Since this insulation will be 12 inches thick the top will sit above the joists but will not cover them.
For any option installing those 2 x 2 furring strips really would be a waste unless the area is very unlevel.
Add thick insulation batts to the attic.
Installing attic insulation is one of the most valuable ways to save energy and keep your home warmer.
You have 2x4 rafters but what are the ceiling joists constructed of.
Is this a stick built arch or do you have web trusses.
I d like to double my ceiling joists to make my attic space easier to work in for electrical plumbing and for lightweight storage.
Are they also 2x4.
Each joist is strong enough to support my weight 175lbs concentrated in a 1 segment of the joist and.
In order to create a deeper cavity for the insulation it will be necessary to attach wood framing to the existing rafters through a process called furring.
Put standard fiberglass insulation that s appropriate for the climate probably r 38 between the joists.
When using fiberglass insulation the pink stuff the attic roof rafter will need to be at least 16 deep.
You say in the attic but not the garage s attic so i m assuming you mean in another structure s attic a hypothetical situation.
If done right blown in cellulose insulation adds a lot of r value in all areas without doing too much work in regards to packing it in like batted insulation.
2x4 s actual size spaced 16 on center running the width of the building uninterrupted with the ends resting on top of the wall top plate.
Batts are long strips of unrolled and unfaced fiberglass insulation.
Put insulation meant for 2x4 framed walls between the joists which will be the same height as the joists then lay a perpendicular layer of attic insulation maybe r 30 on top of them.